Are you getting started with an exercise program? Hoping to improve your existing routines or find new workout options? Did you know that a complete plan consists of three basic elements: aerobic fitness, muscle strength/endurance and flexibility? How do you assess your current fitness level before you begin? How do you know how much exercise you should do, or whether you should see a doctor before you start?

Our Healthy Living channel provides in-depth answers to these questions, along with guidelines to help you develop a fitness program that's right for you. With these exercise and fitness tips, you can learn to gauge how hard and how often you should exercise, and get yourself started on the road to better fitness today.

Q. Why do you use the BMI, and is it useful for weight lifters?

The Body Mass Index (BMI) is a simple way for men and women to estimate body fat based on their height and weight. From the BMI, it is possible to determine your healthy weight range.

One of the limitations of BMI is that it can overpredict overweight or obesity in people who are lean and muscular. For instance, someone who is 5 feet 10 inches tall and weighs 220 pounds, with 12% body fat, would be considered obese based on BMI standards. Obviously, someone with 12% body fat is not obese.

The scientists who developed the BMI guidelines readily admit to this limitation. But their rationale is that most Americans are not lean and muscular and so for most people, the BMI is an accurate assessment of body fat and increased health risk.

It is important to know that people who are classified as overweight or obese can still be healthy as long as they are fit. In one well-known study, fit people with BMIs that classified them as overweight or obese were healthier and lived longer than unfit people who were at normal weight.

The BMI, for the majority of Americans, is the most up-to-date and scientifically sound method available for determining healthy weight.

Q. Does aerobic exercise interfere with muscle gains from weightlifting?

If you're training for an endurance event like a marathon, when you might run 60 miles or more per week, you'll almost always see a decrease in your muscle mass. For most of us, who do more moderate amounts of physical activity, there will be minimal, if any, loss in muscle mass -- so there's nothing to worry about.

If you do plan on lots of aerobic exercise and are concerned about losing muscle, try starting with 20-30 minutes of moderate aerobic exercise (at 50% to 70% of your maximum heart rate) two to three days per week, and see how it goes.

High Blood Pressure and Exercise

A sedentary lifestyle is a major risk factorfor heart and blood
vessel (cardiovascular) disease. For example, people who are less active and
less physically fit have a 30%-50% greater frequency (incidence) of
hypertension (high blood pressure) than their more active peers. Furthermore, clinical trialshave shown that
physical activity may reduce blood pressure in hypertensiveand normotensive(having normal blood pressure) individuals, independent of changes in weight.

Medications have proven to be effective in lowering blood pressure and
protecting against the risk of cardiovascular and kidney(renal) diseases.
However, because of the side effectsand cost of medications, many individuals would prefer to undertake lifestyle modifications to help improve blood pressure as a first-line treatment. In numerous clinical studies, it has been well documented that aerobic exerciseis a suitable
treatment and can even play a roll in the prevention of hypertension. (Aerobic
exercise is vigorous and sustained exercise, such as jogging, swimming,
and cycling.)

Even without changes in body weight, those individuals who participate in aerobic exercise regularly tend to have reductions in resting blood pressure. The blood-pressure reduction does not seem to depend on the frequency or intensity of aerobic exercise or on the type of exercise. That is, the studies have indicated that all forms of exercise seem to be effective in reducing blood pressure. Aerobic exercise appears to have a slightly greater effect on blood pressure in hypertensive individuals than in individuals without hypertension.